基于衍射光栅的高精度干涉星敏感器的理论分析

High accuracy interferometric star tracker based on diffraction grating

为克服传统星敏感器精度与视场、体积、质量等参数难以兼顾的问题,本文研究了一种基于衍射光栅的高精度干涉星敏感器结构。利用角谱理论,建立了星光入射角度与探测器上像点质心位置、像点能量之间的数学模型,确定了干涉星敏感器利用像点质心位置和相对能量分别进行粗定位和精定位的方法及粗精定位结合获得星光入射角度的方法,得出干涉星敏感器单星测量角分辨率和光栅周期、两块光栅之间的距离及像点光强信号电子学细分倍数有关的结论。通过计算机仿真模拟,验证了干涉星敏感器精定位及粗精定位结合的可行性。在光栅周期为50μm,两块光栅距离为50 mm,像点光强信号每变化一个周期采用1024倍电子学细分的情况下,单星测量角分辨率达0.1″,与传统星敏感器相比精度有显著提高。

In order to overcome the problems where traditional star trackers’directional accuracy,field of view,volume,weight and other factors are difficult to balance,we studied a highly accurate interferometric star tracker structure based on a diffraction grating.By using the angular spectrum theory,the mathematical models between the incident angle of starlight,the centroid position of spots,and the relative intensity of spots on the detector were established.Secondly,the methods that estimate a relative coarse position of the target star from a centriod of the spots on the detector,and estimate a relative fine position of the target star from the relative intensity of the spots were determined.Therefore,the relative incident angle of star light was obtained by using successive estimates of the coarse and fine positions.Then,we drew a conclusion that the angle resolution for a single star is affected by the grating period,the distance between the two gratings and the electric subdivision of the intensity signal.Finally,a computer simulation was used to confirm the feasibility of this relative fine positioning technique and this combination technique of coarse positioning and fine positioning.The results show that this measure is praticable,and the angle resolution for a single star can reach 0.1 arc-seconds when the grating period is 50μm,the distance between two gratings is 50 mm and the intensity signal of each period is subdivided by 1024 times.Compared with traditional star trackers,the ac-curacy is improved significantly.